1990-02-01

Thermal Analysis of Multiterminal Assemblies 900700

The steady increase in harness complexity due to the automobile's growing “electrification” has resulted in an increase in the number of electric connections and multibranching joints unprecedented in previous designs. In search for a solution to this problem the automotive industry introduced the so called “electrical center” to a portion of its fleet. An electrical center consists of a multiple stack of boards carrying harness interconnection circuitry together with the necessary terminals and quite often a complete set of fuses and a certain number of relays. The whole electrical center assembly is encapsulated in one housing to facilitate manufacturing and maintenance. Therefore, the unusually high concentration of electric lines and connectors, carrying a relatively high electric current, must be designed with a good understanding of the maximum heat generation potential.The purpose of this paper is to assist in understanding the thermal behavior of proposed automotive “electrical centers” and to provide a computerized heat transfer model which can be used to guide their design from the thermal point of view. A two-dimensional analysis of the temperature distribution in a typical “electrical center” is presented. The results of a computer simulation performed for a proposed simplified geometry provide several important general conclusions regarding the system design. In addition, a simple, reliable computation technique handled by a PC IBM compatible software is proposed which can be used when analyzing transient temperature buildup for various system topologies. An example of a fuse meltdown caused by an electric current surge is carried out and is shown to correlate well with experimental results. results.There is a need within the automotive industry for heat transfer modeling tools which can assist in the design of automotive electrical components, sub-assemblies and assemblies. The advent of electrical centers, introduced by the automotive industry in response to the escalating complexity of the car's harness, created a need for a thorough analysis of the temperature development within the structure in order to avoid overheating. An instructive analysis of the thermal response of the structure heated by the electric energy dissipated in the ohmic components and located in the harsh engine compartment environment can and must be initiated prior to the design process to establish a general set of design rules. Since it is demonstrated here that the analysis of temperature transients can be separated from the more complex steady state, an example of the analysis of a sudden system overload is presented to illustrate the technique which can be used for more comprehensive testing of the system response to various overloading conditions when selecting alternative assembly topologies. Since such simulations require the knowledge of the specific structural arrangement, the presented result has a very limited general meaning, and therefore, illustrates only a general approach to the problem.

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